The present invention and my copending applications relate generally to instruments for dilating a body passage to enable draining a fluid through the passage; and, in particular, the tubular instruments adapted to pass through the urethra to the urinary bladder for (1) dilating a narrowed urethra, (2) withdrawing urine, (3) inserting urethral instruments including retention catheters into the urinary tract or (4) performing urologic surgery.
The present invention specifically relates to a rigid, hollow stylet for insertion within a flexible, hollow catheter having an open tip portion--the stylet cooperates with a filiform to place the catheter in the bladder. The stylet can also be used without the filiform for placement of catheters that do not have open tip portions.
By way of background, the size of most urologic instruments including catheters, filiforms, followers, bougies and sounds is determined by the outer diameter of the instrument. Although there are both American and English scales of measurement, the Charriere or French (F) scale is most frequently used. According to the French scale, the size of a tubular instrument is determined by multiplying the diameter expressed in millimeters (mm) by 3. Thus, a diameter of 8 mm is equal to No. 24 F.
Catheters, as defined herein, are hollow, tubular instruments made of rubber, nylon, silicone, Teflon, woven silk (stiffened by shellac), plastic or metal that are used for drainage of fluid media, specifically urine, from the bladder. Many different types are available from a straight tube for a single insertion to tubes of varying shapes, curves and diameters for specific situations. All catheters, however, have similar functions--to provide drainage, to introduce medications and radiopaque contast media, and to obtain a urine specimen.
Catheters may be nonretentive or retentive. The most frequently used straight, nonretentive catheters are the Robinson and the whistle-tip design which are usually made of natural or latex rubber. The Robinson catheter has a solid rounded tip and may have two, four or six eyes or holes along its side. The whistle-tip catheter has an open tip portion and two eyes, one on the side and one at the semirounded angle of the tip. Robinson catheters have the disadvantage of being nonretentive but are used for a single insertion such as in the collection of a urine specimen or in relieving the patient of acute bladder retention.
Another type of nonretentive urethral catheter is the Coude catheter, also known as the "elbow" or "natural curve" catheter. The term "Coude", of course, refers only to the curve of the catheter tip, that tip usually includes a single eye and may taper to a point or have an olive-shaped enlargement (olive tip). The advantage of this curve is that it can following the contour of the bulbar and prostatic urethra as it curves beneath the symphysis pubis and rides over the bladder neck. Coude catheters are usually made of red rubber, are somewhat stiffer than Robinson catheters and are often impregnated with small amounts of lead for radiographic observation.
The most frequently used retentive catheter for draining the bladder is the Foley type, which comprises two tubes--a larger tube for drainage and a smaller side tube connected to a balloon that is inflated with a fluid after the catheter is positioned. The inflated balloon thus prevents the catheter from slipping out. A Councill catheter is similar to a Foley catheter, but includes an open tip portion that receives a special stylet which can be threadably connected to a filiform. The tip of the Foley and Councill catheter usually includes one or two eyes between the tip and the balloon. The present invention relates to an improved Councill catheter-stylet combination in which the filiform and stylet are not threadably connected.
As stated in my copending application, a catheter can usually be passed through the urethra without incident. Occasionally, however, particularly when the lumen of the urethra is narrowed because of disease or when a large tube such as a cystoscope or a large catheter is to be passed, the urethra may have to be dilated. This is done by inserting and withdrawing a series of progressively larger dilation instruments (dilators).
The most common dilator is a solid smooth metal instrument with a curved tip, called a sound, that looks like a metal catheter. For example, the Van Buren sound is such a solid metal instrument--but it is not intended to be left indwelling.
A bougie can also be used. A bougie is a slender, flexible, cylinder solid instrument having an enlarged tip portion for introduction into the urethra or other tubular organ, usually for the purpose of calibrating and dilating a constricted area.
If the passage is severely constricted, use of a filiform and a follower may be necessary. A filiform is a narrow, solid, somewhat stiff instrument commonly used to traverse a strictured urethra. Various filiform tips can be used, such as a straight, spiral or olive tip. The end of the filiform opposite the tip includes a female threaded portion. The follower, a semi-flexible catheter or bougie with a male threaded tip, is then threadably connected to the threaded portion of the filiform to define a tapered assembly having the appearance of a flexible whip.
The assembly can be guided through the strictured area and followers of an increasing diameter can be attached to the filiform upon withdrawal of the follower from the urethra to further dilate the stricture. As the follower is introduced, the filiform merely coils on itself inside the bladder. The screw-on filiform may have either a male or female thread and, of course, the follower must have a corresponding thread to be of use. Frequently the assembly must be left indwelling, particularly when it is desirable to dilate the urethra gradually over the course of several days. In that case, since the filiform is a solid shaft, eyes are provided in the sides of the catheter follower at the tip end portion to permit the drainage of urine from the bladder.
In a similar manner, a filiform can be threadably connected to a solid metal stylet for passage through the urethra. The stylet can be used to pass a catheter through a strictured urethra. In practice, the solid stylet is inserted within the catheter so that the threaded tip of the stylet extends beyond the open tip portion of the catheter, and the stylet can be threadably connected to the filiform. The filiform, stylet and catheter are then passed through the urethra to the bladder. Once the tip of the catheter is in the bladder, a balloon or an inflatable portion near the tip can be inflated to secure the catheter in position. Thereafter the filiform-stylet assembly is withdrawn.
Problems frequently arise, however, in the use of a threaded filiform-follower (or filiform-stylet) assembly. For example, the threaded connection can break or the follower (or the stylet) can separate from the filiform after insertion. In that case, it is very difficult to extricate the filiform from the bladder. Such removal can be performed endoscopically, or surgery may be required to open the bladder and gain sufficient access for removal. In addition to this serious disadvantage, the currently used threaded assembly is nondisposable and must be sterilized after each use. Moreover, the operation of connecting the threaded portion of the filiform and the follower or the stylet is awkward and time consuming.